It is well known to use the naphtha paraffin product as obtained in a Fischer-Tropsch process as steam cracker feedstock. For example in “The Markets for Shell Middle Distillate Synthesis Products”, Presentation of Peter J. A. Tijm, Shell International Gas Ltd., Alternative Energy '95, Vancouver, Canada, May 2-4, 1995 on page 5, it is mentioned that SMDS naphtha, the Fischer-Tropsch derived naphtha fraction of the Shell MDS process, is used as steam cracker feedstock in for example Singapore.
WO-A-2003062352 discloses a process wherein lower olefins are prepared in a steam cracker furnace designed for petroleum naphtha starting from a Fischer-Tropsch derived gas oil.
US-A-2003/0135077 describes a process wherein a so called Fischer-Tropsch derived syncrude is blended with a sulphur containing petroleum derived naphtha and a treated crude derived fraction boiling above the naphtha boiling range. The petroleum derived naphtha, the Fischer-Tropsch syncrude and the refined heavy petroleum-derived portion are forwarded to a naphtha cracker unit for processing.
US-A-2004/0267076 describes a process wherein a Fischer-Tropsch-derived synthetic naphtha boiling in the gasoline range is subjected to a steam cracker unit for processing. A problem of the state of the art processes is that even when optimizing the propylene yield and ethylene yield the severity of the cracking operation is still relatively high resulting in a high methane yield. Methane is an unwanted by-product of the steam cracker process having only a fuel value.